Method of transmitting data in a mobile communication system

ABSTRACT

Disclosed is a data transmission method in a mobile communication system. The data transmission method through a code sequence in a mobile communication system includes grouping input data streams into a plurality of blocks consisting of at least one bit so as to map each block to a corresponding signature sequence, multiplying a signature sequence stream, to which the plurality of blocks are mapped, by a specific code sequence, and transmitting the signature sequence stream multiplied by the specific code sequence to a receiver.

TECHNICAL FIELD

The present invention relates to a mobile communication system, and moreparticularly, to a method of expanding a code sequence, a structure of arandom access channel and a method of transmitting data in a mobilecommunication system.

BACKGROUND ART

A user equipment uses a random access channel (RACH) to access a networkin a state that the user equipment is not uplink synchronized with abase station. A signal having repetitive characteristic in a time domainis used in the random access channel, so that a receiver easily searchesa start position of a transmission signal. In general, the repetitivecharacteristic is realized by repetitive transmission of a preamble.

A representative example of a sequence for realizing the preambleincludes a CAZAC (Constant Amplitude Zero Auto Correlation) sequence.The CAZAC sequence is expressed by a Dirac-Delta function in case ofauto-correlation and has a constant value in case of cross-correlation.In this respect, it has been estimated that the CAZAC sequence hasexcellent transmission characteristics. However, the CAZAC sequence haslimitation in that maximum N-1 number of sequences can be used for asequence having a length of N. For this reason, a method for increasingavailable bits of the sequence while maintaining the excellenttransmission characteristics is required.

Meanwhile, there are provided various methods for transmitting data froma random access channel by using the CAZAC sequence. Of them, the firstmethod is to directly interpret CAZAC sequence ID to messageinformation. Assuming that data to be transmitted is a preamble, if asufficient number of sequences that can be used as the preamble areprovided, message passing can be performed with only CAZAC sequence IDwithout additional manipulation. However, since a method of transmittingadditional information should be considered in an actual synchronizedRACH, problems occur in that there is difficulty in realizing asufficient number of CAZAC sequence sets, and the cost required forsearch of a receiver increases.

The second method is to simultaneously transmit CAZAC sequence and Walshsequence by using a code division multiplexing (CDM) mode. In this case,CAZAC sequence ID is used as user equipment identification information,and the Walsh sequence transmitted in the CDM mode is interpreted asmessage information. FIG. 1 is a block schematic view illustrating atransmitter for realizing the second method. However, the second methodhas limitation in that even though the Walsh sequence is added to theCAZAC sequence, bits of message that can additionally be obtained areonly log₂ N bits when the Walsh sequence has a length of N.

The third method is to transmit CAZAC sequence and Walsh sequence insuch a way to mix the Walsh sequence with the CAZAC sequence. In thiscase, CAZAC sequence ID is used as user equipment identificationinformation, and the Walsh sequence is interpreted as messageinformation. FIG. 2 is a block diagram illustrating a data processingprocedure at a transmitter for realizing the third method. Howeveraccording t the third method, since the Walsh sequence acts as noise indetection of the CAZAC sequence to cause difficulty in detectingsequence ID, there is limitation in that repetitive sequences should betransmitted to prevent the Walsh sequence from acting as noise indetection of the CAZAC sequence.

The fourth method is to either give orthogonality between blocksconstituting a corresponding sequence by multiplying an exponential termby a CAZAC sequence or directly apply data modulation such as DPSK,DQPSK, D8PSK, etc. In this case, CAZAC sequence ID is used as userequipment identification information, and the modulated sequence isdemodulated and then used as message information. FIG. 3A illustratesdata modulation according to the former method of the fourth method, andFIG. 3B illustrates data modulation according to the latter method ofthe fourth.

Furthermore, the filth method is to transmit CAZAC sequence by attachinga message part to the CAZAC sequence. FIG. 4A illustrates the case wherea message (coded bit) is attached to the CAZAC sequence used as apreamble, and FIG. 4B illustrates the case where a message (coded bit)is attached to a sequence consisting of a predetermined number of blocksto which orthogonality is given.

However, the fourth method and the fifth method have a problem in thatthey are susceptible to change of channel condition.

DISCLOSURE OF THE INVENTION

Accordingly the present invention has been suggested to substantiallyobviate one or more problems due to limitations and disadvantages of therelated art, and an object of the present invention is to provide amethod of transmitting and receiving message between a user equipmentand a base station by using a long sequence to maximize time/frequencydiversity and alleviating performance attenuation due to channel.

Another object of the present invention is to provide a method oftransmitting data through a code sequence in a mobile communicationsystem, in which the quantity of data can be increased and thetransmitted data becomes robust to noise or channel change.

Still another object of the present invention is to provide a method ofsuggesting a structure of an efficient random access channel in amulti-carrier system.

Further still another object of the present invention is to provide amethod of minimizing access time of a user equipment to a random accesschannel in a mobile communication system.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adata transmission method through a random access channel in a mobilecommunication system comprises generating a new code by multiplying acode sequence by an exponential sequence, and transmitting the new codesequence to a receiving side.

In another aspect of the present invention, a data transmission methodby using a code sequence in a mobile communication system comprisesconjugating at least one element included in at least one block of acode sequence divided by at least two blocks to indicate predeterminedinformation, and transmitting the code sequence, in which the at leastone block is conjugated, to a receiving side.

In still another aspect of the present invention, a data transmissionmethod by using a code sequence in a mobile communication systemgenerating a second code sequence indicating predetermined informationby combining at least two first code sequences mapped with at least oneinformation bit, respectively, and transmitting the second code sequenceto a receiving side.

In further still another aspect of the present invention., a codesequence transmission method in a mobile communication system comprisesgenerating a combination code sequence by combining a base code sequenceto at least one code sequence obtained by circular shift of the basecode sequence, and transmitting the combination code sequence to areceiving side.

In further still another aspect of the present invention, a codesequence transmission method in a mobile communication system generatinga repetitive code sequence by repeatedly concatenating a first codesequence at least one or more times, generating a cyclic prefix (CP) bycopying a certain part of a rear end of the repetitive code sequence andconcatenating the copied part to a front end of the repetitive codesequence, and transmitting the repetitive code sequence, in which the CPis generated, to a receiving side.

In further still another aspect of the present invention, a method ofallocating a random access channel (RACH) in a multi-carrier systemcomprises allocating a random access channel to each of at least twoconsecutive frames in a way that frequency bands of the random accesschannels allocated to the at least two consecutive frames are notoverlapped with each other, and transmitting allocation information ofthe random access channels allocated to the at least two consecutiveframes to at least one user equipment.

In further still another aspect of the present invention, a datatransmission method through a code sequence in a mobile communicationsystem mapping each of a plurality of blocks having at least one bit ofa input data stream, respectively to a corresponding signature sequence,multiplying a signature sequence stream, to which the plurality ofblocks are mapped, by a specific code sequence, and transmitting thesignature sequence stream multiplied by the specific code sequence to areceiving side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a data transmission method through arandom access channel in an OFDMA system according to the related art;

FIG. 2 illustrates another example of a data transmission method througha random access channel in an OFDMA system according to the related art;

FIG. 3A and FIG. 3B illustrate still another example of a datatransmission method through a random access channel in an OFDMA systemaccording to the related art;

FIG. 4A and FIG. 4B illustrate further still another example of a datatransmission method through a random access channel in an OFDMA systemaccording to the related art;

FIG. 5 illustrates an example of a structure of a random access channelused in an OFDMA system;

FIG. 6A and FIG. 6B illustrate examples of sending an RACH signal in atime domain or a frequency domain based on a structure of a randomaccess channel of FIG. 5;

FIG. 7 illustrates another example of a structure of a random accesschannel used in an OFDMA system

FIG. 8A and FIG. 8B illustrate still another example of a structure of arandom access channel used in an OFDMA system;

FIG. 9 illustrates a structure of a random access channel according toone embodiment of the present invention;

FIG. 10 illustrates a structure of a random access channel of asub-frame to which RACH pilot is allocated;

FIG. 11 illustrates a repetitive structure of a preamble according toone embodiment of the present invention;

FIG. 12 is a structural view of unit data to illustrate one embodimentof the present invention, which transmits data by using a code sequenceexpanded through conjugation;

FIG. 13 is a flow chart illustrating a procedure of receiving anddecoding data transmitted in a code sequence expanded throughconjugation in accordance with one embodiment of the present invention;

FIG. 14 is a structural view of unit data to illustrate one embodimentof the present invention, which transmits data by using a code sequenceexpanded through grouping;

FIG. 15 is a flow chart illustrating a procedure of receiving anddecoding data transmitted in a code sequence expanded through grouping;

FIG. 16 is a structural view of unit data to illustrate one embodimentof the present invention, which transmits data by using a code sequenceexpanded through grouping and delay processing;

FIG. 17 is a flow chart illustrating a procedure of receiving anddecoding data transmitted in a code sequence expanded through groupingand delay processing;

FIG. 18 is a structural view of unit data to illustrate one embodimentof the present invention, which transmits data by using a code sequenceexpanded through PPM modulation;

FIG. 19 is a flow chart illustrating a procedure of receiving anddecoding data transmitted in a code sequence expanded through PPMmodulation;

FIG. 20A and FIG. 20B are flow charts illustrating a procedure ofperforming synchronization in a random access channel in accordance witha data transmission method of the present invention;

FIG. 21 illustrates a method of transmitting data to a receiver throughsignaling channel in accordance with one embodiment of the presentinvention; and

FIG. 22 illustrates an example of a receiver and a transmitter fortransmitting a preamble and data through RACH, SCH or other channel inaccordance with one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, structures, operations, and other features of the presentinvention will be understood readily by the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

A random access channel (RACH) is used to allow a use equipment toaccess a network in a state that the user equipment is not uplinksynchronized with a base station. A random access mode can be classifiedinto an initial ranging access mode and a periodic ranging access modedepending on an access mode to network. According to the initial rangingaccess mode, the user equipment acquires downlink synchronization andfirst accesses a base station. According to the periodic ranging accessmode, the user equipment connected with a network accesses the networkif necessary. The initial ranging access mode is used to allow the userequipment to synchronize with the network while accessing the networkand receive its required ID from the network. The periodic rangingaccess mode is used to initiate a protocol to receive data from the basestation or when a packet to be transmitted exists.

In particular, the periodic ranging access mode can be classified intotwo types in the 3GPP LTE (long term evolution) system, i.e., asynchronized access mode and a non-synchronized access mode. Thesynchronized access mode is used if an uplink signal is within asynchronization limit when the user equipment accesses the RACH. Thenon-synchronized access mode is used if the uplink signal is beyond thesynchronization limit. The non-synchronized access mode is used when theuser first accesses the base station or synchronization update is notperformed after synchronization is performed. At this time, thesynchronized access mode is the same as the periodic ranging accessmode, and is used when the user equipment accesses the RACH for thepurpose of notifying the base station of the change status of the userequipment and requesting resource allocation.

On the other hand, the synchronized access mode alleviates limitation ofa guard time in the RACH by assuming that the user equipment does notdepart from uplink synchronization with the base station. For thisreason, much more time-frequency resources can be used. For example, aconsiderable amount of messages (more than 24 bits) may be added to apreamble sequence for random access in the synchronized access mode sothat both the preamble sequence and the messages may be transmittedtogether.

A structure of the RACH, which performs a unique function of the RACHwhile satisfying the aforementioned synchronized and non-synchronizedaccess modes will now be described.

FIG. 5 is a diagram illustrating an example of a structure of a randomaccess channel (RACH) used in an OFDMA system. As shown in FIG. 5, it isnoted that the RACH is divided into N number of sub-frames on a timeaxis and M number of frequency bands on a frequency axis depending on aradius of a cell. Frequency in generation of the RACH is determineddepending on QoS (Quality of Service) requirements in a medium accesscontrol (MAC) layer. In general, the RACH is generated per certainperiod (several tens of milli-seconds (ms) to several hundreds of ms).In this case, frequency diversity effect and time diversity effect areprovided in generating several RACHs and at the same time collisionbetween user equipments which access through the RACH is reduced. Thelength of the sub-flame can be 0.5 ms, 1 ms, etc.

In the RACH structure as shown in FIG. 5, a random sub-frame will bereferred to as a time-frequency resource (TFR) which is a basic unit ofdata transmission. FIG. 6A is a diagram illustrating a type of sending arandom access signal to the TFR in a time domain, and FIG. 6Billustrates a type of sending a RACH signal in a frequency domain.

As shown in FIG. 6A, if a random access signal is generated in a timedomain, the original sub-frame structure is disregarded and the signalis aligned through only the TFR. By contrast, as shown in FIG. 6B, incase of the synchronized random access mode, the sub-frame structure ismaintained in the frequency domain and at the same time a random accesssignal to be transmitted to sub-carriers of each OFDM symbol isgenerated. Accordingly, orthogonality can be maintained betweenrespective blocks constituting TFR, and channel estimation can easily beperformed.

FIG. 7 is a diagram illustrating another example of a structure of RACHused in an OFDMA system. As shown in FIG. 7, it is noted that a preamble‘b’ and a pilot ‘a’ are partially overlapped in a TDM/FDM mode and a TDMmode of RACH burst duration of an attached wideband pilot. It is alsonoted that a pilot ‘a’ and a pilot ‘b’ are simultaneously overlappedwith a preamble ‘a’ and the preamble ‘b’ in the TDM/FDM mode and the TDMmode of an embedded wideband pilot. In other words, it is designed thata preamble and a pilot are together transmitted through the RACH, sothat message decoding is easily performed through channel estimation ifmessage is added to the RACH. Alternatively, a wideband pilot is used sothat channel quality information (CQI) of a total of RACH bands can beacquired in addition to a preamble band of the RACH.

FIG. 8A and FIG. 8B are diagrams illustrating another examples of astructure of the RACH used in the OFDMA system.

As shown in FIG. 8A, a preamble is transmitted for a predetermined timeperiod through a frequency band, and a short block duration is providedat a certain period so that a pilot for decoding a preamble istransmitted to a corresponding short block. At this time, the pilottransmission is performed through a part of a total of frequency bands(transmission through 25 sub-carriers corresponding to a middle band ofa total of 75 sub-carriers), so that the pilot can be transmitted to aspecific user equipment under a multi-access environment.

Furthermore, as shown in FIG. 8B, a message to be transmitted and apilot for decoding the message are multiplexed and continue to betransmitted through some frequency bands (for example, 25 middlesub-carrier bands of a total of 75 sub-carrier bands) selected from atotal of frequency bands. Accordingly, respective user equipments whichperform multi-access can be identified by allocating some frequencybands at different frequencies.

FIG. 9 is a diagram illustrating a structure of RACH according to oneembodiment of the present invention.

Generally, frequency in generation of the RACH is determined dependingan QoS requirements in a MAC layer The RACH is generated at a variableperiod (several ms to several hundreds of ms) depending on requirementsof a cell. The RACH can be generated in a time domain or a frequencydomain as described above with reference to FIG. 6A and FIG. 6B. In theembodiment of FIG. 9, the structure of the RACH corresponds to the casewhere a random access signal is generated in the frequency domain.

Referring to FIG. 9, in this embodiment, to overcome a drawback of along interval required for retry when the user equipment fails to accessthe RACH a corresponding RACH resource is dispersed in each frame withinone period if frequency in generation of the RACH and the quantity ofoverhead are determined. The number of frames included in one period canfreely be determined as occasion demands. At this time, it is preferablethat the RACH is divisionally arranged so as to be uniformly distributedfor each frequency band with respect to a plurality of framesconstituting one period. However, position on the time axis may bechanged without change of position on the frequency axis and vice versadepending on specific requirements (synchronized action or decrease ofinter-cell interference) of a cell or if a system band is small. Also,arrangement of any one of frequency and time may be changed to obtainthe minimum interval between the RACHs arranged in each frame.

In the embodiment of FIG. 9, the network should notify the userequipment of position information of the allocated RACH resource. Inother words, the network can notify each user equipment of frequency andtime information occupied by the RACH resource allocated for each frameincluded in one period, and each user equipment can try random accessthrough the allocated RACH resource by using the position informationfrom the network. The position information of the RACH resource of eachframe can be expressed by sub-carrier offset, the number ofsub-carriers, timing offset, and the number of symbols. However, if theRACH information on each frame is expressed by the above fourparameters, it may be undesirable in that the quantity of theinformation can be increased. Accordingly, a method of decreasing thequantity of the information for expressing the position information ofthe RACH allocated on each frame is required. The position informationof the RACH can be transmitted through a broadcast channel (BCH) orother downlink control channel.

As one method, a method using a hopping pattern may be considered. Thehopping pattern means a pattern consisting of information indicatingfrequency domains of the RACH resource allocated to each frame withinone period. In other words, in the embodiment of FIG. 9, since the RACHresource is divisionally arranged so as to be uniformly distributed foreach frequency band with respect to a plurality of frames constitutingone period, an indicator which indicates a frequency band that can beallocated to each frame as the RACH resource is previously determined,and the frequency band of the RACH resource allocated to each framewithin one period can be notified through a pattern of the indicatorwhich indicates a corresponding frequency band.

For example, if four frames are used as one period in a system whichuses a total of bands of 10 MHz, the position of the RACH includessub-bands having an interval of 25 MHz as one RACH frequency band (bandsmaller than 1.25 MHz or 2.5 MHz). At this time, a total of bandsconsist of four sub-bands, wherein the respective sub-bands aredesignated by indicators, which indicate each sub-band as 1, 2, 3 and 4in due order from a high frequency band to a low frequency band. In thisway, the frequency band position information of the RACH resourceallocated to all frames within one period can be expressed by patternsconfigured by the above indicators, for example 2, 3, 1, 4. The hoppingpattern may be configured differently or equally depending on eachframe. Time information of the RACH resource allocated to each framewithin one period can generally be expressed by timing offset and thenumber of symbols. At this time at least any one of the timing offsetand the number of symbols may be fixed to decrease the quantity of theinformation. For example, if it is previously scheduled that the timingoffset and the number of symbols for the RACE resource of each frame arefixed, the network only needs to transmit the hopping pattern to notifythe user equipment of the position information of the RACH resource ofall frames within one period.

If each sub-band is narrow or considering influence of interferencebetween user equipments, hopping patterns for all frames may be setequally. In this case, the network only needs to notify the userequipment of a frame period.

Hereinafter, the procedure of transmitting uplink data from the userequipment to the base station by using the structure of the RACH asshown in the embodiment of FIG. 9 will be described. In this case, datatransmission is performed through the RACH among reverse common channelsconsisting of a plurality of frames.

First of all, the user equipment tries to access the dispersed RACHincluded in the current frame to transfer its information to the basestation. If the user equipment successfully accesses the RACH, the userequipment transmits preamble data through the corresponding RACH.However, if the user equipment fails to access the RACH, the userequipment tries to access the RACH divisionally arranged in the frame ofthe next order. At this time, the RACH included in the frame of the nextorder is preferably arranged in a frequency band different from that ofthe RACH of the previous frame if the frequency band is not sufficientlywide or there are no specific requirements (inter-cell interference orlimitation in action range of user equipment). Also, the above accessprocedure continues to be performed in the frame of the next order untilthe user equipment successfully accesses the RACH.

Meanwhile, in case of the synchronized RACH, the sub-frame of each framepreferably includes a short block to which a pilot for the userequipment which has accessed the corresponding RACH is allocated. Atleast one RACH pilot and access pilot may be allocated to the shortblock at a predetermined pattern. In other words, the user equipmentwhich has accessed the RACH should know channel information to receive achannel from the base station. The channel information may be set inRACH pilot within an uplink short block. The base station allocates aproper channel to the user equipment through the corresponding RACHpilot. Meanwhile, if the user equipment which accesses the RACH notifiesthe base station of information of channel quality as to whether theuser equipment is preferably allocated with which channel through theRACH pilot, a favorable channel can be allocated to the user equipmentduring scheduling, whereby communication of good quality can bemaintained.

Accordingly, the RACH pilot that can be used for the user equipmentwhich accesses the RACH is separately allocated to the sub-frame whichincludes RACH. Thus, the user equipment which accesses the RACH sends apreamble to the base station through the corresponding RACH and alsosends a pilot for transmission of channel quality information to thedesignated RACH pilot. The RACH pilot is a sequence designated dependingon a preamble, and it is preferable that the user equipments, which usedifferent preamble sequences, use different RACH pilot sequences ifpossible or select RACH pilot of different sub-carriers or partiallyoverlapped sub-carriers.

FIG. 10 is a diagram illustrating a structure of a random access channelof a sub-frame to which the RACH pilot is allocated. It is noted thateach sub-frame includes at least one short block, to which at least oneRACH pilot and access pilot are allocated at a predetermined pattern. Inthis case, the RACH pilot exists in the frequency band of the allocatedRACH and other system bands. In this embodiment, it has been describedthat two short blocks exist per one frame and the RACH pilot istransmitted to the short blocks. However, the present invention is notlimited to such embodiment, and various modifications can be made withinthe apparent range by those skilled in the art.

As described above, it has been described that preamble, synchronizationtiming information including pilot information, uplink resourceallocation information and message such as uplink data can betransmitted through the RACH of various structures. It will he apparentthat the data transmission method according to the embodiments of thepresent invention can be used in the RACH and other channels.

Meanwhile, the preamble and the message may separately be transmittedthrough the RACH. Alternatively, the message may be transmitted by beingimplicitly included in the preamble. One embodiment of the presentinvention relates to a method of transmitting a preamble through thelatter transmission manner. In one embodiment of the present invention acode sequence more expanded than that of the related art can be used foreffective transmission of the preamble. Hereinafter, a method ofimproving CAZAC sequence according to one embodiment of the presentinvention for effective transmission of the preamble will be described.

Since the receiver should search a start position of a transmissionsignal in the random access channel, it is generally designed that atransmission signal has a specific pattern in a time domain. To thisend, the preamble is transmitted repeatedly or a certain interval ismaintained between sub-carriers in a frequency domain to obtainrepetitive characteristics in the time domain, thereby identifying timesynchronization.

In the former case, the preamble represents, a reference signal used forthe purpose of initial synchronization setting, cell detection,frequency offset, and channel estimation. In a cellular mobilecommunication system a sequence having good cross-correlationcharacteristic is preferably used for repetitive transmission of thepreamble. To this end, binary hardamard code or poly-phase CAZACsequence may be used. Particularly, the CAZAC sequence has beenestimated that it has excellent transmission characteristics as it isexpressed by a Dirac-Delta function in case of auto-correlation and hasa constant value in case of cross-correlation.

The CAZAC sequence can be classified into GCL sequence (Equation 1) andZadoff-Chu sequence (Equation 2) as follows.

$\begin{matrix}{{{c\left( {{k;N},M} \right)} = {{\exp\left( {- \frac{j\; \pi \; {{Mk}\left( {k + 1} \right)}}{N}} \right)}\mspace{14mu} {for}\mspace{14mu} {odd}\mspace{14mu} N}}{{c\left( {{k;N},M} \right)} = {{\exp\left( {- \frac{j\; \pi \; {Mk}^{2}}{N}} \right)}\mspace{14mu} {for}\mspace{14mu} {even}\mspace{14mu} N}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \\{{{c\left( {{k;N},M} \right)} = {{\exp\left( \frac{j\; \pi \; {{Mk}\left( {k + 1} \right)}}{N} \right)}\mspace{14mu} {for}\mspace{14mu} {odd}\mspace{14mu} N}}{{c\left( {{k;N},M} \right)} = {{\exp\left( \frac{j\; \pi \; {Mk}^{2}}{N} \right)}\mspace{14mu} {for}\mspace{14mu} {even}\mspace{14mu} N}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the above Equations, it is noted that if the CAZAC sequence has alength of N, actually available sequences are limited to N-1 number ofsequences. Accordingly, it is necessary to increase the number of CAZACsequences to efficiently use them in an actual system.

For example, a method of expanding the number of available sequences by1 is suggested by providing an improved CAZAC sequence p(k) in such away to multiply a CAZAC sequence c(k) by a predetermined modulationsequence m(k). In other words, assuming that Zadoff-Chu sequence is usedas the CAZAC sequence, the CAZAC sequence c(k), the modulation sequencem(k) and the improved CAZAC sequence p(k) can be defined by thefollowing: Equations 3, 4, and 5, respectively.

$\begin{matrix}{{{CAZAC}\mspace{14mu} {sequence}\text{:}}{{c\left( {{k;N},M} \right)} = {\exp\left( \frac{j\; \pi \; {{Mk}\left( {k + 1} \right)}}{N} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack \\{{{Modulation}\mspace{14mu} {sequence}\text{:}}{{m(k)} = {\exp\left( {\frac{j2\pi\delta}{N}k} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack \\{{{Improved}\mspace{14mu} {CAZAC}\mspace{14mu} {sequence}\mspace{14mu} \left( {{or}\mspace{14mu} {improved}\mspace{14mu} {preamble}} \right)\text{:}}{{p(k)} = {{{c(k)}*{m(k)}} = {\exp\left( {{\frac{{j\pi}\; M}{N}{k\left( {k + 1} \right)}} + {\frac{{j2\pi}\; \delta}{N}k}} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

The improved CAZAC sequence p(k) maintains auto-correlation andcross-correlation characteristics of the CAZAC sequence. The followingEquation 6 illustrates auto-correlation characteristic of p(k), and itis noted from the Equation 6 that the final result is a Dirac-deltafunction. In particular, if the modulation sequence m(k) is a sequencehaving a certain phase, it is characterized in that the modulationsequence m(k) always maintains the auto-correlation characteristic.

$\begin{matrix}{\mspace{644mu} \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack} & \; \\\begin{matrix}{{{ad}(d)} = {\sum\limits_{k}{\exp\left( {{\frac{{j\pi}\; M}{N}\left( {k + d} \right)\left( {k + d + 1} \right)} + {\frac{j2\pi\delta}{N}\left( {k + d} \right)}} \right)}}} \\{{\exp\left( {{{- \frac{{j\pi}\; M}{N}}{k\left( {k + 1} \right)}} - {\frac{j2\pi\delta}{N}k}} \right)}} \\{= {\sum\limits_{k}{\exp\left( {{\frac{{j\pi}\; M}{N}\left( {{2{dk}} + {d\left( {d + 1} \right)}} \right)} + {\frac{j2\pi\delta}{N}d}} \right)}}} \\\left. {= {{\exp\left( {\frac{j2\pi\delta}{N}d} \right)}{\sum\limits_{k}{\exp\left( {{\frac{{j\pi}\; M}{N}\left( {{2{dk}} + {d\left( {d + 1} \right)}} \right)} + {\frac{j2\pi\delta}{N}d}} \right)}}}} \right) \\{= \left\{ \begin{matrix}1 & {d = 0} \\0 & {d \neq 0}\end{matrix} \right.}\end{matrix} & \;\end{matrix}$

Furthermore, the following Equation 7 illustrates cross-correlationcharacteristic of p(k).

$\begin{matrix}{\mspace{644mu} \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack} & \; \\\begin{matrix}{{{cc}(d)} = {\sum\limits_{k}{\exp\left( {{\frac{{j\pi}\; \left( {M + x} \right)}{N}\left( {k + d} \right)\left( {k + d + 1} \right)} + {\frac{j2\pi\delta}{N}\left( {k + d} \right)}} \right)}}} \\{{\exp\left( {{{- \frac{{j\pi}\; M}{N}}{k\left( {k + 1} \right)}} - {\frac{j2\pi\delta}{N}k}} \right)}} \\{= {\sum\limits_{k}{\exp\left( {\frac{{j\pi}\; x}{N}\left( {k + d} \right)\left( {k + d + 1} \right)} \right)}}} \\{{\exp\left( {{\frac{{j\pi}\; M}{N}\left( {k + d} \right)\left( {k + d + 1} \right)} + {\frac{j2\pi\delta}{N}\left( {k + d} \right)}} \right)}} \\{{\exp\left( {{{- \frac{{j\pi}\; M}{N}}{k\left( {k + 1} \right)}} - {\frac{j2\pi\delta}{N}k}} \right)}} \\{= {\sum\limits_{k}{\exp\left( {\frac{{j\pi}\; x}{N}\left( {k + d} \right)\left( {k + d + 1} \right)} \right)}}} \\{{\exp\left( {{\frac{{j\pi}\; M}{N}\left( {{2{dk}} + {d\left( {d + 1} \right)}} \right)} + {\frac{j2\pi\delta}{N}d}} \right)}} \\{= {{\exp\left( {\frac{{j\pi}\; M}{N}{d\left( {d + 1} \right)}} \right)}{\sum\limits_{k}{\exp \left( {\frac{{j\pi}\; x}{N}\left( {k + d} \right)\left( {k + d + 1} \right)} \right)}}}} \\{{\exp\left( {\frac{{j2\pi}\; {dM}}{N}k} \right)}}\end{matrix} & \;\end{matrix}$

In this case, although Equation 7 seems to be similar to Equation 6, itis noted that in view of summation term, auto-correlation is expressedby sum of exponential but cross-correlation is expressed by the productof two sequences. The first term is another CAZAC sequence of which seedvalue is x, and the second term is a simple exponential function. Thesum of the product of two sequences is equal to obtaining a coefficientof the exponential function, and its value is equal to a value obtainedby converting the CAZAC sequence of which seed value is x into afrequency domain and extracting a value from the frequency position ofexponential.

Since the CAZAC sequence has auto-correlation of Dirac-deltacharacteristic, if it undergoes Fourier transform, it maintainsauto-correlation characteristic of Dirac-delta of a constant amplitudeeven in the transformed area. For this reason, if values of specificpositions are extracted from the frequency domain, their sizes are 1 andequal to each other but their phases are different from each other.Accordingly, if this result is added to the Equation 7 to obtaincross-correlation, the obtained cross-correlation can briefly beexpressed by the following Equation 8.

$\begin{matrix}{\mspace{644mu} \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack} & \; \\\begin{matrix}{{{cc}(d)} = {{\exp\left( {{\frac{{j\pi}\; M}{N}{d\left( {d + 1} \right)}} + {\frac{j2\pi\delta}{N}d}} \right)}{\sum\limits_{k}{\exp\left( {\frac{{j\pi}\; x}{N}\left( {k + d} \right)\left( {k + d + 1} \right)} \right)}}}} \\{{\exp\left( {\frac{{j2\pi}\; {dM}}{N}k} \right)}} \\{= {{\exp\left( {{\frac{{j\pi}\; M}{N}{d\left( {d + 1} \right)}} + {\frac{j2\pi\delta}{N}d}} \right)}{C\left( {{{dM}/N};x} \right)}}}\end{matrix} & \;\end{matrix}$

It is noted from the Equation 8 that since C(dM/N;x) always has a sizeof 1 and an exponential term also has a size of 1, the cross-correlationis always fixed at 1.

After all, characteristics of the related art CAZAC sequence can bemaintained by the Equation 5 and at the same time the number of codescan be increased. This means that the result in the area where theexponential terms are multiplied is equal to applying circular shift tothe Fourier transformed area, and multiplying exponential sequences inthe time domain is equal to performing circular shift in the frequencydomain.

In other words, it is noted that if correlation between two sequencesp(k;M,N,d1) and p(k;M,N,d2) of which seed values are equal to each otheris obtained, impulse occurs in a point where a delay value d incross-correlation reaches d1-d2. Although design of the improvedsequence as above has the same result as that of circular shift of theCAZAC sequence, this embodiment of the present invention is advantageousin that the result can be obtained by a simple procedure such asmultiplying two exponential sequences without Fourier inverse transformafter Fourier transform and circular shift.

Hereinafter, a method of improving data transmission reliability of apreamble by performing predetermined data processing for the related artcode sequence and a method of expanding a length of a code sequence whendata are simultaneously transmitted will be described. If the CAZACsequence is used as the code sequence, the CAZAC sequence expanded bythe above method is preferably used. However, the CAZAC sequence is notnecessarily limited, to the CAZAC sequence expanded by the above methodand the related art CAZAC sequence may be used.

First of all, a structure of transmission data, i.e., preamble, which iscommonly applied to the embodiments of the present invention, will bedescribed.

In a 3GPP LTE (Long Term Evolution) system, a transmitter can repeatedlytransmit the same sequence two times or more so as to allow a receiverto easily detect transmission data or improve additional detectionperformance increase of spreading gain). Accordingly, since the receiveronly needs to detect repetitive patterns regardless of the type of thereceived sequence, it can simply identify time position of a userequipment which accesses the RACH and improve detection performance.

FIG. 11 is a diagram illustrating a structure of a preamble according toone embodiment of the present invention. In an orthogonal frequencydivisional transmission system, a cyclic prefix (CP) is used, in whichthe last part of OFDM symbol is copied and then prefixed to the OFDMsymbol to compensate a multi-path loss in signal transmission.Accordingly, if the OFDM symbol consists of two repetitive preambles, apart of the preamble of the later order is copied in the first part byCP to enable compensation of the multi-path loss for the correspondingpreamble. Also, the CP is advantageous in that it is easy to identifyuser equipments which access different RACHs in case of CAZAC havinggood periodic correlation.

Since inter-symbol interference does not occur even though a singlesequence is transmitted by prefixing CP thereto instead of repetitivetransmission of sequence, a predetermined receiving algorithm can berealized in the frequency domain without any problem. However, if thereceiver realizes a receiving algorithm in the time domain with neitherrepetitive transmission nor CP, the receiver should detect all kinds ofcode sequences to identify user equipments which access the RACH. Inthis respect, the preamble is preferably realized by a structure of arepetitive pattern. At this time, whether to realize a repetitionpattern can be determined depending on a data rate supported by thesystem or the number of repetitive times can be determined if arepetitive pattern is realized. For example, to support a minimum datarate supported by the system, RACH preamble can repeatedly betransmitted one or more times depending on the length of the sequence.

First to fourth embodiments which will be described later relate to adata processing method of a sequence constituting the structure of thepreamble. In these embodiments, data transmitted to the receiver couldbe the structure of the preamble of FIG. 11 or a partially omittedstructure (having neither repetitive transmission nor CP). Although itis assumed that the CAZAC sequence is used as the code sequence for datatransmission, the code sequence is not necessarily limited to the CAZAC,sequence. Every sequence having excellent transmission characteristic,such as Hadarmad code and gold code, can be used as the code sequence.

First Embodiment

To transmit data, a landmark that can be identified is generallyrequired for a transmission signal constituting data. In thisembodiment, conjugation is used as the landmark. Since a phase variationwidth between a conjugated transmission signal and other transmissionsignal is very great, interference between transmission signalsdecreases, whereby reliability of data transmission can be improved inspite of influence of channel.

FIG. 12 illustrates a method of transmitting data through conjugationaccording to one embodiment of the present invention. In the embodimentof FIG. 12, one CAZAC sequence is divided into four blocks, and ‘0’ or‘1’ indicates whether to perform conjugate for each block. For example,it may be promised that a block which is not conjugated is expressed by‘0’, and a block which is conjugated is expressed by ‘1. ’ In this way,one CAZAC sequence can express information of 4 bits. In other words, ifone CAZAC sequence is divided into N number of blocks, information of Nbits can be expressed.

At this time, in a single CAZAC sequence of a long length correspondingto a length of transmission data, a part of the single CAZAC sequence,which corresponds to a specific block having a value of 1, may beconjugated. Also, in a plurality of CAZAC sequences of a short lengthcorresponding to each block length of transmission data, a CAZACsequence corresponding to a specific block having a value of 1 may beconjugated.

FIG. 13 is a diagram illustrating an example of a method of receivingand decoding the sequence transmitted through conjugation from thetransmitter in accordance with one embodiment of the present invention.

It is preferable that the transmitter always allocates a value of 0 tothe first block of the transmission data so that the first block is usedas a reference later. Accordingly, the receiver identifies sequence IDfor the received first block (S1101), and then measures a peak by usingonly the corresponding block (S1102). Next, the receiver identifiessequence IDs for the first and second blocks (S1103), and then measuresa peak by using the first and second blocks together. At this time,since it is unclear whether the sequence of the second block is in theconjugated status, the receiver respectively measures a peakcorresponding to the case where the corresponding block is conjugated(S1104) and a peak corresponding to the case where the correspondingblock is not conjugated (S1105), and then selects greater one of the twopeaks (S1106). Subsequently, the receiver identifies sequence IDs forthe first to third blocks (S1107), and then measures a peak by using thefirst to third blocks together. In this case, since it is unclearwhether the sequence of the third block is in the conjugated status, thereceiver respectively measures a peak corresponding to the case wherethe corresponding block is conjugated (S1108) and a peak correspondingto the case where the corresponding block is not conjugated (S1109), andthen selects greater one of the two peaks (S1110). In this way, decodingis performed for the first block to the last block so that the originaldata is finally decoded.

Second Embodiment

FIG. 14 is a diagram illustrating a method of transmitting data using asequence according to another preferred embodiment of the presentinvention. Although data transmission is performed by change of thesequence in the first embodiment, in this embodiment, a type of asequence for expressing one block is divided into a sequence (firstsequence) for a block value of and a sequence (second sequence) for ablock value of ‘1,’ and the first and second sequence are grouped. Inthis case, since the receiver detects only sequence ID (ID of the firstsequence or ID of the second sequence) for each block, the receiver isless affected by noise or channel.

All sequences are expressed by one group “{c₀(k;M_(i)), c₁(k;M_(j))}” bygrouping two sub-sequences (first sequence and second sequence) (i and jare integers different from each other). In this case, c₀(k;M_(i)) isthe first sequence for the block value of 0 (or bit value) andc₁(k;M_(i)) is the second sequence for the block value of 1. At thistime, a CAZAC sequence of a long length corresponding to a length oftransmission data may be used as each sub-sequence constituting eachgroup. Alternatively, a CAZAC sequence of a short length correspondingto each block length of transmission data may be used as eachsub-sequence constituting each group.

Meanwhile, the receiver identifies sequence ID of each block andidentifies a type of the sequence (first sequence or second sequence)for each block from a sequence ID set consisting of the identifiedsequence IDs. At this time, the type of the sequence for each block canbe expressed by group ID. In other words, in this embodiment, since itis assumed that code values of each block can be expressed by 0 and 1,two types of the sequence for each block or two types of group ID areobtained. The code values of each block can be restored through groupID. This decoding procedure will be described in detail with referenceto FIG. 15.

The receiver identifies sequence ID of each block constituting acorresponding sequence if the sequence is received (S1501), and measuresa peak for a sequence ID set consisting of the identified sequence IDs(S1502). In this case, two peaks having high frequency in generation areselected (S1503) so that sequences which generate the correspondingpeaks are identified as the first sequence and the second sequenceconstituting the group. At this time, if the first sequence and thesecond sequence are expressed by predetermined group IDs, respectively,first group ID indicating a code value of 0 and second group IDindicating a code value of 1 can be identified. After all, group ID ofeach block can be identified through the step S1503 (S1504), and thusthe code value of each block can be identified (S1508).

If sequence IDs that can not identify group ID exist due to erroroccurring during the decoding procedure, peaks are searched for a set ofcorresponding sequence IDs (S1505), and among the peaks, two powerfulpeaks are detected (S1506) so that group IDs are again identified fromthe detected powerful peaks (S1507). Subsequently, code values of thecorresponding blocks can be identified from the identified group IDs(S1508).

Third Embodiment

FIG. 16 is a diagram illustrating a method of transmitting data using asequence according to another preferred embodiment of the presentinvention.

If the second embodiment is more expanded, a total number of data bitsthat can be transmitted through one group can be increased. For example,if two sequences are defined as one group like the second embodiment,data of 1 bit per block can be transmitted. If four sequences aredefined as one group, data of 2 bits per block can be transmitted. Ifeight sequences are defined as one group, data of 3 bits per block canbe transmitted. However, since a plurality of sequences are grouped anddefined as one set, a problem occurs in that if the length of eachsequence is short, the number of groups that can be selected isdecreased in proportion to the short length of each sequence.

Accordingly, it is necessary to expand the length of the sequence toincrease the number of groups that can be selected. To this end, in thisembodiment, the length of the sequence for each block is expanded whilerespective sequences are multi-overlapped as shown in FIG. 16B andindependence is maintained owing to transmission delay between theoverlapped sequences.

Referring to FIG. 16( a), a data value of 2 bits is given to each block.Accordingly, a sequence group for each block consists of four differentCAZAC sequences. Since each CAZAC sequence constituting the sequencegroup should identify four values, a group size should be increasedcorrespondingly. However, in this case, a problem occurs in that thenumber of groups that can be used by each base station is decreased.Accordingly, as shown in FIG. 16, the length of each CAZAC sequence isexpanded as much as need be while a predetermined delay is given to eachCAZAC sequence during data transmission, whereby independence ismaintained between the respective CAZAC sequences.

Meanwhile, the receiver identifies ID of a corresponding block based onthe order of each CAZAC sequence represented in the time/frequencydomain, and its method of decoding a code value from corresponding blockID is almost identical with that of the second embodiment. Hereinafter,a data decoding procedure of the receiver will be described in detailwith reference to FIG. 17.

The receiver identifies sequence ID of each block constituting acorresponding sequence if the sequence is received (S1701), and measuresa peak for a sequence ID set consisting of the identified sequence IDs(S1702). In this embodiment, since one block expresses two bits, first,second, third and four sequences which express 00, 01, 10, 11 form onegroup. Accordingly, the receiver should select 4 peaks having highfrequency in generation as a result of measurement (S1703). In thiscase, the selected peaks are respectively mapped to the first, second,third and fourth sequences in accordance with the order represented inthe time/frequency domain. Also, if the first sequence to the fourthsequence are expressed by predetermined group IDs, respectively, firstgroup ID indicating a code value of 00, second group ID indicating acode value of 01, third group ID indicating a code value of 10, andfourth group ID indicating a code value of 11 can be identified. Afterall, group ID of each block can be identified through the step S1703(S1704), and thus the code value of each block can be identified(S1708).

If sequence IDs that can not identify group ID exist due to erroroccurring during the decoding procedure, peaks are again searched for aset of corresponding sequence IDs (S1705), and among the peaks, fourpowerful peaks are detected (S1706) so that group IDs are againidentified from the detected powerful peaks (S1707). Subsequently, codevalues of the corresponding blocks can be identified from the identifiedgroup IDs (S1708).

Fourth Embodiment

FIG. 18 is a diagram illustrating a method of transmitting data using asequence according to another preferred embodiment of the presentinvention.

In the case that the second embodiment and the third embodiment are moreexpanded, the signal position is changed through pulse positionmodulation (PPM) so that the length of the sequence can be expandedlogically. The PPM originally transmits data with relative pulse delaybut PPM based on start position of the sequence is used in thisembodiment.

If bits of data to be transmitted are determined, the base stationselects a sequence to be used for transmission of corresponding data anddetermines a length of a block for applying PPM to a correspondingsequence and a length of a duration constituting each block. A sequencecorresponding to each block is separately required when a preamble isgenerated. However in this embodiment, since circular shift equivalentto a specific duration within a specific block constituting acorresponding sequence is applied for the same sequence, the respectivesequences are originally the same as one another but are identified fromone another by circular shift.

For example, assuming that one sequence length is divided into ourblocks (block 1 to block 4) and each block is expressed by 2 bits, eachblock is again divided into four durations (duration 1 to duration 4) toexpress values of “00, 01, 10, 11.” At this time, four durationsincluded in one block are used as start identification positions ofcircular shift for a sequence corresponding to a corresponding block. Ifa preamble to be transmitted has a total length of 256, block 1 can havea circular shift value of 0˜63, block 2 64˜127, block 3 128˜195, andblock 4 196˜255. If a specific, sequence to be used for transmission ofthe preamble is determined and “00” is transmitted through block 1,sequence 1 undergoes circular shift so that a start position is arrangedin duration 1 (0˜15) of block 1. If “10” is transmitted to block 2,sequence 2 undergoes circular shift so that a start position is arrangedin duration 3 (96˜411) of block 2. In this way, circular shift isapplied for the other blocks and then the respective sequences (sequence1 to sequence 4) are grouped into one to generate one preamble. In thiscase, the number of blocks can be generated from 1 to every randomnumber. Also, a minimum unit of circular shift can be limited to morethan a certain value considering channel or timing error.

Meanwhile, the receiver identifies respective sub sequences (sequence 1to sequence 4) constituting corresponding sequences by data processingthe transmitted sequences, and searches a start position of each of theidentified sequences to perform data decoding. This will be described indetail with reference to FIG. 19.

If a sequence is received in the receiver (S1901), the receiver detectsID of the corresponding sequence (S1903) and performs full correlationthrough predetermined data processing for a total of received signals(received sequence) by using the detected result (S1905). At this time,a full search algorithm or a differential search algorithm can be usedfor detection of the sequence ID.

Since the received signal is transmitted from the transmitter bygathering a plurality of sequences, the signal which has undergone thecorrelation includes a plurality of peaks. In this embodiment, fourpeaks are detected, and the receiver determines whether each of thedetected peaks corresponds to which one of block 1 to block 4 and alsocorresponds to which duration of a corresponding block (S1909) to decodebit order and bit value of the original data (S1911).

The method of effectively transmitting the preamble sequence and messagethrough the RACH has been described as above. Finally, a procedure oftransmitting a preamble from a user equipment (UE) to a base station(Node-B) and performing synchronization between both the user equipmentand the base station will be described based on two embodiments. FIG.20A and FIG. 20B illustrate the two embodiments.

In the embodiment of FIG. 20A, synchronization is performed in such amanner the user equipment accesses the base station only once. In otherwords, if the user equipment transmits a preamble and a messingincluding information required for synchronization to the base station(S2001), the base station transmits timing information to the userequipment (S2003) and at the same time allocates a resource fortransmission of uplink data (S2005). The user equipment transmits theuplink data to the base station through the allocated resource (S2007).

In the embodiment of FIG. 20B, for synchronization, the user equipmentaccesses the base station twice. In other words, if the user equipmenttransmits a preamble to the base station (S2011), the base stationtransmits timing information to the user equipment and at the same timeallocates a resource for a request of scheduling (S2013). The userequipment transmits a message for a request of scheduling to the basestation through the allocated resource (S2015). Then, the base stationallocates a resource for transmission of uplink data to the userequipment (S2017). In this way, the user equipment transmits to theuplink data to the base station through the secondly allocated resource(S2019).

FIG. 21 is a diagram illustrating a method of transmitting data to areceiver through a signaling channel in accordance with one embodimentof the present invention.

Since the receiver should search a start position of a transmissionsignal in actually realizing the random access channel, it is generallydesigned that the random access channel has a specific pattern in thetime domain. To this end, a preamble sequence may be used so that therandom access signal originally has a repetitive pattern. Alternatively,a certain interval may be maintained between sub-carriers in thefrequency domain to obtain repetitive characteristics in the timedomain. Accordingly, the access modes of FIG. 6A and FIG. 6B arecharacterized in that the start position of the transmission signalshould easily be searched in the time domain. To this end, the CAZACsequence is used. The CAZAC sequence can be classified into GCL sequence(Equation 1) and Zadoff-Chu sequence (Equation 2).

Meanwhile, a specific sequence of a long length is preferably used totransmit unique information of the user equipment or the base stationthrough RACH (Random Access Channel) or SCH (Synchronization Channel).This is because that the receiver easily detects corresponding ID andmore various kinds of sequences can be used to provide convenience forsystem design.

However, if message is transmitted with corresponding ID at a sequenceof a long length, since the quantity of the message is increased by log₂function, there is limitation in message passing with ID only when thesequence exceeds a certain length. Accordingly, in this embodiment, thesequence is divided by several short blocks, and a short signaturesequence corresponding to data to be transmitted to each block of thesequence is used instead of specific manipulation such as conjugation ornegation.

Referring to FIG. 21, the sequence is divided into a predeterminednumber of blocks, and a short signature sequence corresponding to datato be transmitted is applied for each of the divided blocks. A longCAZAC sequence is multiplied by combination of the blocks for which theshort signature sequence is applied, whereby a final data sequence to betransmitted to the receiver is completed.

In this case, assuming that the short signature sequence consists offour signatures, the following signature sets can be used. Also, ifthere is difference between respective data constituting the signaturesets, any other signature set may be used without specific limitations

1) Modulation values: {1+j, 1−j, −1−j, −1+j}

2) Exponential sequence: {[exp(jw₀n)], [exp(jw₁n)], [exp(jw₂n)],[exp(jw₃n)]}, where n=0 . . . Ns, and Ns is a length of each block

3) Walsh Hadamard sequence: {[1111], [1−11−1], [11−1−1], [1−1−11]},where, if the length Ns of each block is longer than 4, each sequence isrepeated to adjust the length.

Examples of the long CAZAC sequence that can be used in the embodimentof FIG. 21 include, bat not limited to, one GCL, CAZAC sequence,Zadoff-Chu CAZAC sequence, and a sequence generated by concatenation oftwo or more short GCL or Zadoff-Chu CAZAC sequences having the samelength or different lengths.

The aforementioned manner of applying a short signature sequence fordata transmission and reception to the long CAZAC sequence isadvantageous in that it is less affected by channel than the related artmodulation method of transmission data and performance is littledecreased even though the number of bits constituting one signature isincreased.

FIG. 22 illustrates an example of a receiver and a transmitter fortransmitting a preamble and data through RACH, SCH or other channel byusing the aforementioned manner.

Since the number of bits can be increased in accordance with increase ofsignatures, channel coding can be applied for the transmitter. Ifchannel coding is performed, time/frequency diversity can be obtainedthrough an interleaver. Also bit to signature mapping can be performedto minimize a bit error rate. In this case, Gray mapping can be used.The sequence which has undergone this procedure is mixed with CAZAC andthen transmitted.

The receiver detects CAZAC ID, and calculates a log-likelihood ratio(LLR) for each of bits. Then, the receiver decodes transmission datathrough a channel decoder. Considering complexity according to sequencesearch of the receiver configured as shown in FIG. 22, the transmitterpreferably uses an exponential sequence as a signature sequence. In thiscase, the receiver can simply search CAZAC ID through phase differenceFourier Transform. Afterwards, the receiver can again simply calculateLLR from the signature through Fourier Transform.

According to the present invention, the structure on the frequencyaxis/time axis of the RACH can be identified more definitely. Also sincethe RACH resource is divisionally distributed for each frame, eventhough the user equipment fails to access a specific RACH, the userequipment can directly access RACH of the next frame, whereby access tothe base station is improved. Moreover, the user equipment can easilyaccess the RACH even in case of a traffic area of which QoS condition isstrict.

Furthermore, according to the present invention, since information istransmitted and received between the user equipment and the base stationby using the code sequence, time/frequency diversity can be maximized,and performance attenuation due to influence of channel can bealleviated through the signature manner.

According to the present invention, since the total length of thecorresponding sequence can be used with maintaining the advantage of thecode sequence according to the related art, data transmission can beperformed more efficiently. Also, since the code sequence undergoespredetermined data processing, the quantity of information to betransmitted can be increased and the transmitted data becomes robust tonoise or channel.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a wireless communication systemsuch as a mobile communication system or a wireless Internet system.

What is claimed is:
 1. A method of transmitting a preamble sequence viaa random access channel (RACH) in a mobile communication system, themethod comprising: generating said preamble sequence in a time domainaccording to resources permitted for the RACH; and transmitting thepreamble sequence via the resources to a receiving side, wherein theresources are given regardless of a time domain unit of an OFDM(Orthogonal Frequency Divisional Multiplexing) symbol duration within asubframe.
 2. The method of claim 1, wherein generating said preamblesequence comprises: generating a specific sequence from a ConstantAmplitude Zero Auto Correlation (CAZAC) sequence; repeating saidspecific sequence at least one time; and concatenating a cyclic prefix(CP) to a front end of the repeated sequence, said cyclic prefix beingidentical to a part of a rear end of the specific sequence.
 3. Themethod of claim 2, further comprising applying a cyclic shift to saidspecific sequence.
 4. The method of claim 3, wherein a value of saidapplied cyclic shift is determined as an integer multiple of apredetermined circular shift unit.
 5. The method of claim 3, wherein avalue of said applied cyclic shift is used as additional information. 6.The method of claim 3, wherein applying said cyclic shift comprisesmultiplying said specific sequence by an exponential sequence.
 7. Atransmitter for transmitting a preamble sequence via a random accesschannel (RACH) in a mobile communication system, the transmittercomprising: a preamble generation unit configured to generate saidpreamble sequence in a time domain according to resources permitted forthe RACH; a transmission unit configured to transmit the preamblesequence via the resources to a receiving side, wherein the resourcesare given regardless of a time domain unit of an OFDM (OrthogonalFrequency Divisional Multiplexing) symbol duration within a subframe. 8.The transmitter of claim 7, wherein said preamble generation unit isfurther configured to generate a specific sequence from a ConstantAmplitude Zero Auto Correlation (CAZAC) sequence, to repeat saidspecific sequence at least one time, and to concatenate a cyclic prefix(CP) to a front end of the repeated sequence, said cyclic prefix beingidentical to a part of a rear end of the specific sequence.
 9. Thetransmitter of claim 8, wherein said preamble generation unit is furtherconfigured to apply a cyclic shift to said specific sequence.
 10. Thetransmitter of claim 9, wherein a value of said applied cyclic shift isdetermined as an integer multiple of a predetermined circular shiftunit.
 11. The transmitter of claim 9, wherein a value of said appliedcyclic shift is used as additional information.
 12. The transmitter ofclaim 9, wherein said preamble generation unit is further configured toapply said cyclic shift by multiplying said specific sequence by anexponential sequence.